In the current glass fiber manufacturing art, binders and silane coupling agents are used for sizing and reinforcement of glass fibers. They are required to manage high-speed coating to glass fiber substrates associated with productivity improvements, anti-fluffing, a strength buildup that allows for formation of thin-film plates for multilayer capacitors as final products, and a strength buildup of FRP used in bath tabs or the like. It is also desired to improve strength when glass fibers are sized with unsaturated polyester resin or epoxy resin sizing agents as molding resins.
Under these circumstances, the glass fiber manufacturing art needs surfactants having surface tension and contact angle reducing capabilities for facilitating penetration of binders and silane coupling agents into glass fiber substrates.
Acetylene glycol type surfactants such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol and ethylene oxide adducts thereof are currently used as wetting agents in glass fiber-treating compositions because of a good balance in their ability to lower both static and dynamic surface tensions, substantial elimination of the drawbacks of existing nonionic and anionic surfactants, and even anti-foaming ability. On use of binders, for example, vegetable oil, cationic surfactant, the above-mentioned surfactant for imparting penetrability to the substrates, and optionally wax are added to starch (serving as binder) to suppress fluffing. As performance and productivity improvements mark further advances, it is desired to further improve wetting, dispersing and similar properties.
As to the use of silane coupling agents, JP-A 7-315888 discloses a sizing agent comprising an epoxy resin, an epoxy resin curing agent, a silane coupling agent containing an epoxysilane, and a nonionic surfactant in the form of an ethylene oxide adduct of bisphenol A or polyethylene glycol fatty acid ester. However, these nonionic surfactants are sometimes inferior in penetration because of their high static surface tension as compared with silicone surfactants.
As performance and productivity improvements mark further advances, it is desired to further improve wetting, dispersing and similar properties.
Also, silicone surfactants have been commercially used as penetrating agents in the glass fiber manufacturing art while taking advantage of their low surface tension and low contact. Although the silicone surfactants have good leveling, wetting and dispersing properties, their extraordinary foaming ability invites many practical troubles due to foams. Specifically, drawbacks like coating failure and irregularities on coating surface arise probably because of foams generated during coating and a high dynamic surface tension. This gives rise to a problem that no sufficient strength is exerted when unsaturated polyester resins or epoxy resins as molding resins are applied to glass fibers.    Prior Art 1: JP-A 7-315888    Prior Art 2: JP-A 2000-290549    Prior Art 3: JP-A 2000-327787